[U-Boot] [PATCH 3/5] net: Make copy_filename() accept NULL src

[Joe Hershberger]

On Thu, Jul 5, 2018 at 6:49 AM, Alexander Graf <agraf at suse.de> wrote:
> On 07/04/2018 06:18 PM, Joe Hershberger wrote:
>>
>> On Wed, Jul 4, 2018 at 4:25 AM, Alexander Graf <agraf at suse.de> wrote:
>>>
>>> On 07/04/2018 02:36 AM, Joe Hershberger wrote:
>>>>
>>>> Rather than crashing, check the src ptr and set dst to empty string.
>>>>
>>>> Signed-off-by: Joe Hershberger <joe.hershberger at ni.com>
>>>
>>>
>>> Wouldn't it make more sense to check for the existence outside at the
>>> caller's side? That way it's much easier to see what really is happening.
>>
>> It's much easier to allow NULL so that we can directly pass the return
>> result of getenv().
>
>
> I know, and I see how it looks insanely smart and simple today. Until you
> realize that the amazing "copy_filename" function doesn't touch the target
> at all if it gets passed in NULL. And all of that implicitly. So implicitly
> it will leave the old value in the filename if nothing is set in env.

I think you are mis-reading the code. If src is NULL, it will set
dst[0] = '\0';  I think the behavior is quite reasonable.

> Imaging you're trying to read the code 4 years from now. Will you remember
> all of the side effects of copy_filename()? Imagine you're someone who's new
> to the code and doesn't know all the implicit side effects of its functions.
> Will you understand what is going on at a glimpse?

That's an argument for documentation... and anyway, yes, I think the
function is sensible and I would expect it to do what it does.

-Joe